<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      color: red;
      font-size: 30px;
      background-color: orange;
    }

    .div-one {
      color: blue;
      font-size: 30px;
      background-color: fuchsia;
    }
  </style>
</head>

<body>
  <div>我是div元素</div>
  <div class="div-one">我也是div元素</div>
</body>

</html>